Use of poor-quality groundwater has become inevitable for irrigation to compensate rapidly increasing water demands in many arid and semiarid regions. Salinity and sodicity are the principal soil and water quality concerns in such areas. Many saline–sodic and sodic soils have saline or saline–sodic subsurface drainage waters. Amelioration of these soils needs a source of calcium (Ca2+) that can replace the excess exchangeable sodium (Na+). Most of these soils, however, contain calcite (CaCO3) of extremely low solubility. The native calcite does not supply adequate levels of Ca2+ for soil amelioration as do other chemical amendments. Phytoremediation may help ameliorate such soils through cultivation of certain crops tolerant to ambient soil salinity and sodicity. This amelioration strategy works through plant root action to help dissolve CaCO3 to supply adequate Ca2+ without the application of an amendment. During a 3-year field experiment conducted under irrigated conditions, we evaluated phytoremediation against soil application of gypsum and farm manure, and water treatment with sulphuric acid on a calcareous saline–sodic soil (pHs=8.0–8.4, ECe=24–32 dS m−1, SAR=57–78, CaCO3=45–50 g kg−1 for the top 0.15 m depth; Calcic Haplosalids). A saline–sodic water (EC=2.9–3.4 dS m−1, SAR=12.0–19.4, RSC=4.6–10.0 mmolc l−1, SARadj=15.6–18.4) was used to irrigate the rice (Oryza sativa L.) and wheat (Triticum aestivum L.) crops grown in rotation. Active desalinisation and desodication processes were observed in all the treatments. After the final wheat crop, the 1.2 m soil profile ECe was 7±0.5 dS m−1 and SAR was 15±2 with non-significant treatment differences, indicating comparable soil amelioration effect of phytoremediation with other treatments. Better crop yields were obtained from the manure-treated plots, owing to its annual addition to the soil that possibly improved soil fertility. Phytoremediation needed minimum capital input because no initial investment was made to purchase the amendments. 相似文献
Nutrients and trace elements were determined in the foliage of nine tree species grown in mixtures of pulverized fuel ash (PFA) and gypsum. No serious macronutrient deficiencies were observed. Treatments with PFA consistently increased foliar levels of boron, potassium and molybdenum, and the poor performance of some tree species in pure PFA was attributed to boron toxicity. Gypsum hindered the uptake of boron when mixed with PFA, however, and co-disposal of the two wastes could be used to minimize problems associated with boron toxicity. 相似文献
Tillage practices on sloping ground often result in unsustainable soil losses impairing soil functions such as crop productivity, water and nutrients storage, and soil organic carbon (SOC) sequestration. A sloping olive grove (10%) was planted in shallow gypsiferous soils in 2004. It was managed by minimum tillage; the most frequent management practice in central Spain. The consequences of erosion were studied in soil samples (at 0–10, 10–20, and 20–30 cm depths) by analyzing SOC, available water and gypsum content, and by detecting spectral signatures using an ASD FieldSpecPro® VIS/NIR-spectroradiometer. The Brightness index (BI), Shape index (FI), and Normalized Difference Vegetation Index (NDVI) were derived from the ASD spectral signatures and from remote sensing (Sentinel-2 image) data. The development of these young olive trees was estimated from the measured diameter of the trunks (17 ± 18 cm diameter). In 20–30 cm of the soil, the carbon stock (38 ± 18 Mg ha−1) as well as the available water content (12 ± 6%) was scarce, affecting the productivity of the olive grove. The above-mentioned indices obtained from the laboratory samples and the pixels of the Sentinel-2 image were significantly (p < 0.01) correlated, with a correlation coefficient of around 0.4. The BI was related to the gypsum content and the slope of the plot. The FI was related to the carbon and water contents. The NDVI derived from the satellite image identified the influence of soil degradation on the trees and the carbon content. The spatial-temporal changes of the indices might help in tracking soil changes over time. 相似文献
Understanding the interactions between soil and the organisms that are conducive to decreasing sediment runoff is a great concern on high-elevation ski trails. Intense rainfalls on steep slopes combined with soil formed on gypsum result in recurrent erosion. This study was conducted in the northern French Alps to determine the abilities of species: (1) to make mounds and (2) to trap sediment and thereby to control erosion at the slope scale. We also investigated relevant above-ground plant characteristics related to those abilities. Sediment runoff or deposition was investigated at small and large spatial scales. We assessed whether hoof prints in soil reflect sediment runoff at the slope scale by trapping sediment. Populations of plants growing on two slope angles (25° and 35°) and three vegetation cover densities (15%, 35%, 60%) were surveyed. An experiment was also conducted to measure the sediment deposit upslope of target species and over three months during the autumn. Small mounds were found upslope of the plant and sediment deposit measurements showed that they resulted from a sedimentation process. Nevertheless the species differed in their capacity to make mounds. Sesleria caerulea and Festuca alpina had the highest amount of sediment deposition over the experimental period. Among the plant characteristics, plant length was positively correlated with mound area, while the roundness index of the canopy was negatively correlated with mound height. Mound formation was also positively related to the number of tillers or shoots. Sediment accumulation in cow hoof prints was linked to runoff that occurred at the slope scale. Low deposition in hoof prints means low sediment runoff or a large deposition on mounds, due to the increase in vegetation cover. All the findings stressed that understanding the processes in action at larger scales requires studying processes at smaller scales. 相似文献
Soil compaction is one of the major problems facing modern agriculture. Overuse of machinery, intensive cropping, short crop rotations, intensive grazing and inappropriate soil management leads to compaction. Soil compaction occurs in a wide range of soils and climates. It is exacerbated by low soil organic matter content and use of tillage or grazing at high soil moisture content. Soil compaction increases soil strength and decreases soil physical fertility through decreasing storage and supply of water and nutrients, which leads to additional fertiliser requirement and increasing production cost. A detrimental sequence then occurs of reduced plant growth leading to lower inputs of fresh organic matter to the soil, reduced nutrient recycling and mineralisation, reduced activities of micro-organisms, and increased wear and tear on cultivation machinery. This paper reviews the work related to soil compaction, concentrating on research that has been published in the last 15 years. We discuss the nature and causes of soil compaction and the possible solutions suggested in the literature. Several approaches have been suggested to address the soil compaction problem, which should be applied according to the soil, environment and farming system.
The following practical techniques have emerged on how to avoid, delay or prevent soil compaction: (a) reducing pressure on soil either by decreasing axle load and/or increasing the contact area of wheels with the soil; (b) working soil and allowing grazing at optimal soil moisture; (c) reducing the number of passes by farm machinery and the intensity and frequency of grazing; (d) confining traffic to certain areas of the field (controlled traffic); (e) increasing soil organic matter through retention of crop and pasture residues; (f) removing soil compaction by deep ripping in the presence of an aggregating agent; (g) crop rotations that include plants with deep, strong taproots; (h) maintenance of an appropriate base saturation ratio and complete nutrition to meet crop requirements to help the soil/crop system to resist harmful external stresses. 相似文献